U.S. patent application number 10/694258 was filed with the patent office on 2005-04-28 for wheel position indicator.
Invention is credited to Brown, Gregory P., Hulme, Ian, Kapteyn, Jeffrey S., Turner, Marcus.
Application Number | 20050087121 10/694258 |
Document ID | / |
Family ID | 34522566 |
Filed Date | 2005-04-28 |
United States Patent
Application |
20050087121 |
Kind Code |
A1 |
Brown, Gregory P. ; et
al. |
April 28, 2005 |
Wheel position indicator
Abstract
A wheel position indication system for a vehicle comprising a
steerable wheel, a wheel position indicator and a controller. The
wheel position indicator has an on state and an off state. The
wheel position indicator provides a visual indication of the
position of the steerable wheel when the wheel position indicator
is in the on state. The wheel position indicator does not provide a
visual indication of the position of the steerable wheel when the
wheel position indicator is in the off state. The controller
selectively alters the wheel position indicator between the on
state and the off state. The controller places the wheel position
indicator into the on state when the vehicle is in a predetermined
driving condition and places the wheel position indicator into the
off state when the vehicle is not in the predetermined driving
condition.
Inventors: |
Brown, Gregory P.;
(Dearborn, MI) ; Kapteyn, Jeffrey S.; (Grand
Rapids, MI) ; Turner, Marcus; (Coventry, GB) ;
Hulme, Ian; (Learnington Spa, GB) |
Correspondence
Address: |
PRICE, HENEVELD, COOPER, DEWITT & LITTON, LLP
695 KENMOOR S.E.
P. O. BOX 2567
GRAND RAPIDS
MI
49501-2567
US
|
Family ID: |
34522566 |
Appl. No.: |
10/694258 |
Filed: |
October 27, 2003 |
Current U.S.
Class: |
116/31 ;
340/438 |
Current CPC
Class: |
B62D 15/02 20130101;
B62D 15/0205 20130101 |
Class at
Publication: |
116/031 ;
340/438 |
International
Class: |
B60Q 001/42 |
Claims
We claim:
1. A method of indicating a position of a steerable wheel of a
vehicle comprising: providing a wheel position indicator having an
on state and an off state, the wheel position indicator providing a
visual indication of the position of the steerable wheel when the
wheel position indicator is in the on state, the wheel position
indicator not providing a visual indication of the position of the
steerable wheel when the wheel position indicator is in the off
state; placing the wheel position indicator into the on state when
the vehicle is in a predetermined driving condition; and placing
the wheel position indicator into the off state when the vehicle is
not in the predetermined driving condition.
2. The method of indicating the position of the steerable wheel of
the vehicle of claim 1, wherein: the predetermined driving
condition is an off road driving condition.
3. The method of indicating the position of the steerable wheel of
the vehicle of claim 1, wherein: the predetermined driving
condition occurs when the steerable wheel has a slip angle above or
equal to a predetermined amount.
4. The method of indicating the position of the steerable wheel of
the vehicle of claim 1, wherein: the visual indication of the
position of the steerable wheel includes a display mechanically
connected to a steering column of the vehicle.
5. The method of indicating the position of the steerable wheel of
the vehicle of claim 1, further including: determining a position
of the steering column.
6. The method of indicating the position of the steerable wheel of
the vehicle of claim 1, wherein: the visual indication includes a
digital display.
7. The method of indicating the position of the steerable wheel of
the vehicle of claim 1, wherein: the position of the steerable
wheel includes an angle of the steerable wheel relative to a
longitudinal axis of the vehicle.
8. The method of indicating the position of the steerable wheel of
the vehicle of claim 1, wherein: the position of the steerable
wheel includes a left or a right position of the steerable wheel
relative to a longitudinal axis of the vehicle.
9. A wheel position indication system for a vehicle, comprising: a
steerable wheel; a wheel position indicator having an on state and
an off state, the wheel position indicator providing a visual
indication of the position of the steerable wheel when the wheel
position indicator is in the on state, the wheel position indicator
not providing a visual indication of the position of the steerable
wheel when the wheel position indicator is in the off state; a
controller selectively altering the wheel position indicator
between the on state and the off state; wherein the controller
places the wheel position indicator into the on state when the
vehicle is in an off road condition and places the wheel position
indicator into the off state when the vehicle is not in the off
road condition.
10. The wheel position indication system for the vehicle of claim
9, wherein: the visual indication of the position of the steerable
wheel includes a display mechanically connected to a steering
column of the vehicle.
11. The wheel position indication system for the vehicle of claim
9, further including: a shutter wheel having apertures adjacent a
periphery of the shutter wheel, the shutter wheel being adapted to
be connected to a steering column; wherein the controller
communicates with sensors reading light emitted through the
apertures of the shutter wheel to determine the position of the
steerable wheel.
12. The wheel position indication system for the vehicle of claim
9, wherein: the visual indication includes a digital display.
13. The wheel position indication system for the vehicle of claim
9, wherein: the position of the steerable wheel includes an angle
of the steerable wheel relative to a longitudinal axis of the
vehicle.
14. The wheel position indication system for the vehicle of claim
9, wherein: the position of the steerable wheel includes a left or
a right position of the steerable wheel relative to a longitudinal
axis of the vehicle.
15. A wheel position indication system for a vehicle, comprising: a
steerable wheel; a wheel position indicator having an on state and
an off state, the wheel position indicator providing a visual
indication of the position of the steerable wheel when the wheel
position indicator is in the on state, the wheel position indicator
not providing a visual indication of the position of the steerable
wheel when the wheel position indicator is in the off state; a
controller selectively altering the wheel position indicator
between the on state and the off state; wherein the controller
places the wheel position indicator into the on state when the
steerable wheel has a slip angle above or equal to a predetermined
amount and places the wheel position indicator into the off state
when the steerable wheel has a slip angle below the predetermined
amount.
16. The wheel position indication system for the vehicle of claim
15, wherein: the visual indication of the position of the steerable
wheel includes a display mechanically connected to a steering
column of the vehicle.
17. The wheel position indication system for the vehicle of claim
15, further including: a shutter wheel having apertures adjacent a
periphery of the shutter wheel, the shutter wheel being adapted to
be connected to a steering column; wherein the controller
communicates with sensors reading light emitted through the
apertures of the shutter wheel to determine the position of the
steerable wheel.
18. The wheel position indication system for the vehicle of claim
15, wherein: the visual indication includes a digital display.
19. The wheel position indication system for the vehicle of claim
15, wherein: the position of the steerable wheel includes an angle
of the steerable wheel relative to a longitudinal axis of the
vehicle.
20. The wheel position indication system for the vehicle of claim
15, wherein: the position of the steerable wheel includes a left or
a right position of the steerable wheel relative to a longitudinal
axis of the vehicle.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to an indicator, and in
particular to a wheel position indicator for a motor vehicle.
[0002] When driving off road, on a slippery surface, in a deep rut,
etc., the driver of the motor vehicle may have turned the front
wheels of the vehicle in a direction different than the direction
of travel of the vehicle. For example, the front wheels may
experience wheel slip if the driver is driving on a slippery
surface or may be in a rut that forces the vehicle to travel along
the length of the rut. However, when the road friction of the road
surface increases or the depth of the rut is reduced, the vehicle
may rapidly yaw when the vehicle begins to follow the direction of
the wheels. In some situations, the driver of the vehicle may not
know the direction of the wheels and may be unprepared for the
rapid yaw of the vehicle when the vehicle leaves the slippery
surface or the deep rut. Accordingly, an apparatus for notifying
the driver of the angle of the front wheels is desired.
SUMMARY OF THE INVENTION
[0003] One aspect of the present invention is to provide a method
of indicating a position of a steerable wheel of a vehicle which
comprises providing a wheel position indicator having an on state
and an off state. The wheel position indicator provides a visual
indication of the position of the steerable wheel when the wheel
position indicator is in the on state, but does not provide a
visual indication of the position of the steerable wheel when the
wheel position indicator is in the off state. The method further
includes placing the wheel position indicator into the on state
when the vehicle is in a predetermined driving condition and
placing the wheel position indicator into the off state when the
vehicle is not in the predetermined driving condition.
[0004] Another aspect of the present invention is to provide a
wheel position indication system for a vehicle. The wheel position
indication system includes a steerable wheel, a wheel position
indicator and a controller. The wheel position indicator has an on
state and an off state. The wheel position indicator provides a
visual indication of the position of the steerable wheel when the
wheel position indicator is in the on state. The wheel position
indicator does not provide a visual indication of the position of
the steerable wheel when the wheel position indicator is in the off
state. The controller selectively alters the wheel position
indicator between the on state and the off state. The controller
places the wheel position indicator into the on state when the
vehicle is in an off road condition and places the wheel position
indicator into the off state when the vehicle is not in the off
road condition.
[0005] Yet another aspect of the present invention is to provide a
wheel position indication system for a vehicle comprising a
steerable wheel, a wheel position indicator and a controller. The
wheel position indicator has an on state and an off state. The
wheel position indicator provides a visual indication of the
position of the steerable wheel when the wheel position indicator
is in the on state. The wheel position indicator does not provide a
visual indication of the position of the steerable wheel when the
wheel position indicator is in the off state. The controller
selectively alters the wheel position indicator between the on
state and the off state. The controller places the wheel position
indicator into the on state when the steerable wheel has a slip
angle above or equal to a predetermined amount and places the wheel
position indicator into the off state when the steerable wheel has
a slip angle below the predetermined amount.
[0006] Accordingly, the wheel position indicator will indicate the
position of the steerable wheel to notify the driver of the vehicle
that the steerable wheel may not be in the position contemplated by
the driver. The driver will then be able to respond adequately when
the steerable wheel reacts according its proper direction of
travel. The wheel position indicator is easy to implement, capable
of a long operable life, and particularly adapted for the proposed
use.
[0007] These and other features, advantages, and objects of the
present invention will be further understood and appreciated by
those skilled in the art by reference to the following
specification, claims and appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic view of a vehicle embodying the
present invention.
[0009] FIG. 2 is a schematic view of a digital visual indicator
representing a visual indication of a steerable wheel of the
vehicle.
[0010] FIG. 3 is a plan view, partially cut away, of a steering
sensor comprising a component part of a wheel indication system of
the present invention.
[0011] FIG. 4 is a cross sectional view of the steering sensor of
the present invention taken along the line 4-4 of FIG. 3.
[0012] FIG. 5A illustrates the output wave forms of the detectors
employed in the steering sensor illustrated in FIGS. 3 and 4 for
clockwise rotation.
[0013] FIG. 5B illustrates the output wave forms of the detectors
employed in the steering sensor illustrated in FIGS. 3 and 4 for
counterclockwise rotation.
[0014] FIG. 6 is a truth table illustrating the outputs of
detectors A and B illustrated in FIGS. 3-5 as the steering sensor
of the present invention is rotated counterclockwise and
clockwise.
[0015] FIG. 7 is a schematic view of a first visual indicator
directly connected to a steering column of the vehicle.
[0016] FIG. 8 is a schematic view of a second visual indicator
directly connected to a steering column of the vehicle.
[0017] FIG. 9 is a schematic view of a third visual indicator
directly connected to a steering column of the vehicle.
[0018] FIG. 10 is a schematic view of a vehicle having active front
steering embodying the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0019] For purposes of description herein, it is to be understood
that the invention may assume various alternative orientations,
except where expressly specified to the contrary. It is also to be
understood that the specific devices and processes illustrated in
the attached drawings, and described in the following specification
are simply exemplary embodiments of the inventive concepts defined
in the appended claims. Hence, specific dimensions and other
physical characteristics relating to the embodiments disclosed
herein are not to be considered as limiting, unless the claims
expressly state otherwise.
[0020] Referring to FIG. 1, reference number 10 generally
designates a vehicle embodying the present invention. The vehicle
10 includes a wheel position indication system for indicating a
position of a steerable wheel 12 of the vehicle 10. The vehicle
comprises the steerable wheel 12, a wheel position indicator 14 and
a controller 16. The wheel position indicator 14 has an on state
and an off state. The wheel position indicator 14 provides a visual
indication of the position of the steerable wheel 12 when the wheel
position indicator 14 is in the on state. The wheel position
indicator 14 does not provide a visual indication of the position
of the steerable wheel 12 when the wheel position indicator 14 is
in the off state. The controller 16 selectively alters the wheel
position indicator 14 between the on state and the off state. The
controller 16 places the wheel position indicator 14 into the on
state when the vehicle 10 is in a predetermined driving condition
and places the wheel position indicator 14 into the off state when
the vehicle 10 is not in the predetermined driving condition.
[0021] In the illustrated example, the vehicle 10 includes a pair
of the steerable wheels 12 that pivot about a pivot point 20 with
respect to a vehicle frame 22. Each wheel 12 defines a steering
angle 24 between a longitudinal axis 26 of the vehicle and a
central travel axis 40 of each wheel 12. It should be noted that
while the steering angle 24 is defined by the pivotal movement of
each of steerable wheels 12, the steering angle 24 may be defined
by pivotable rear wheels if the vehicle is so equipped, and/or any
other pivotable wheels.
[0022] The illustrated vehicle 10 also includes a steering column
36 rotatable in a direction represented by an arrow 42, and
operable to receive a driver input control angle from an operator
of the vehicle 10 via a steering wheel 44. The steering column 36
is operably linked to the steerable wheels 12 via a rack-and-pinion
system 46 that includes a rack 48 and a pinion gear 50, a pair of
drag links 52, and a steering arm 54. Although the present example
utilizes a rack-and-pinion steering system, it should be noted that
other steering systems compatible with the vehicle 10 described
herein may be utilized.
[0023] In the present invention, the visual indication of the
position of the steerable wheel could be an analog or digital
visual indicator in the dashboard of the vehicle 10. The visual
indicator that represents the position of the steerable wheel could
be by way of a continuous scale, discrete settings or a left/right
indicator. Discrete settings, together with a low pass filter, may
be preferred when the vehicle experiences many oscillations such
that the indicator provides a steady output. FIG. 2 illustrates a
digital visual indicator 56 including a circle 58 with a plurality
of digital lines displaying the central travel axis 40 of each
wheel 12, with a vertical line 60 (shown in phantom) at the top of
the circle (i.e., twelve o'clock position) representing the central
travel axis 40 being parallel with the longitudinal axis 26 of the
vehicle 10. In the illustrated example, the steerable wheel 12 is
displayed as a line 62 positioned relative to the vertical line 62
approximately equal to the position of steering angle 24 relative
to the longitudinal axis 26 of the vehicle. It is contemplated that
the digital display indicator could include a left/right indicator
or a numerical value, with positive numbers representing the
degrees that the wheel 12 is turned to the right and negative
numbers representing the degrees that the wheel 12 is turned to the
left (or vice versa). Those skilled in the art will appreciate
other digital means of representing the position of the steerable
wheel 12.
[0024] When the digital visual indicator 56 is used in the wheel
position indicator system, the steering position indicated can use
a steering sensor to determine the position of the steerable wheel
12. In a preferred embodiment as illustrated in FIGS. 3-6, the
steering sensor 18 includes means for measuring the absolute
steering position, which represents the angular excursion of the
steerable wheel from a center position, which is determined by the
steering sensor in conjunction with the control module and means.
As shown in FIGS. 3 and 4, the steering sensor 18 comprises shutter
wheel 28, attached to a steering column 36. The steering column
rotates in unison with the steering wheel as the steering wheel is
turned by the driver of the vehicle. Shutter wheel 28 has a
plurality of apertures 30, in this case 40 in number, which
apertures serve to trigger the activity of detectors A and B as the
shutter wheel is rotated with the steering system of the vehicle.
Because there are 40 apertures contained within the shutter wheel
28, the steering sensor provides a signal 80 times during one
revolution of the steering wheel and, as a result, each of the 80
signals or steps indicates 4.5.degree. of rotation of the steering
system. Those skilled in the art will appreciate that to attain
greater control accuracy, a shutter having a greater number of
apertures could be used. This considerably increases the resolution
and correspondingly the precision of the sensor.
[0025] As shown in FIG. 4, each of the detectors A and B includes a
light emitting diode (LED) 32 and a photo diode 34. The combination
of the LED and the photo diode is used to detect movement of the
shutter wheel 28 and, hence, the steering system. This is possible
because the photo diodes have two states, i.e., they are bistable.
A conducting state occurs whenever light from the paired LED passes
through one of the apertures 30 in the shutter wheel and impinges
upon the photo diode. The output of the detector circuit then rises
to approximately 5 volts. A non-conducting state exists whenever
the shutter wheel blocks the transmission of light between the LED
and the photo diode. As shown in FIG. 5A, clockwise rotation of the
shutter wheel 28 produces a wave form pattern for the detectors A
and B in which detector A undergoes its transition prior to
detector B. In other words, detector A leads detector B.
[0026] On the other hand, as shown in FIG. 5B, counterclockwise
rotation of the steering sensor produces a wave form pattern for
the detectors A and B in which detector A undergoes its transition
after detector B and detector A thus lags detector B. The outputs
of detectors A and B are fed into the control module and in this
manner a control module is allowed to track the direction of the
steering system's rotation.
[0027] FIG. 6 is a tabulation of the wave forms shown in FIGS. 5A
and 5B in a digital format. In conventional fashion, the
approximately 5 volts maximum output of the detectors A and B is
treated as a logical "1," while the zero output state is treated as
a logical "0." FIG. 6 shows each of the possible logic pair states
which could be output by detectors A and B. The pairs are arranged
in the order in which they will be received by the control module
for both counterclockwise and clockwise rotation. As seen in FIG.
6, counterclockwise rotation is read from the bottom of the figure
to the upper part of the figure, with clockwise rotation being read
from the top of the tabulation to the lower part of the tabulation.
With the optical sensor herein described, the detectors A and B are
preferably running the entire time that the steering lock of the
vehicle is not engaged. Alternatively, the error checking is
preferably carried out following a beginning of sensing by the
detectors A and B, typically after the engine is started. Those
skilled in the art will appreciate that other steering angle
sensors could be utilized, including, but not limited to, magnetic
and geared sensors. It should also be noted that existing steering
angle sensors fitted to the vehicle for other purposes (e.g.,
Dynamic Stability Control) could be used together with controllers
and displays described herein.
[0028] FIGS. 7-9 illustrate visual indicators directly connected to
the steering column 36 of the vehicle. In each of the visual
indicators illustrated in FIGS. 7 and 8, the visual indicator
includes a circular display 64 in the dashboard of the vehicle 10
that represents the angle of the steerable wheel 12 via a line 66,
wherein the line is vertical, or in the twelve o'clock position.
The line 66 will rotate with the steering column 36 to represent
the angle of the wheel 12. In the visual indicator in FIG. 7, a
drive belt 68 extends between the circular display 64 and the
steering column 36 to rotate with the steering column 36. In the
visual indicator in FIG. 8, an idler gear 70 is positioned between
the steering column 36 and the circular display 64 and rotates the
circular display 64 with rotation of the steering column 36. In the
visual indicator of FIG. 9, an L-shaped steering direction switch
72 is positioned adjacent the steering column 36 and a protrusion
74 on the steering column 36 alternatively switches the direction
switch 72 as the steering column 36, and therefore the steerable
wheel 12, moves from a left position (shown in phantom) to a right
position (and vice versa). The visual indicator in FIG. 9 is an
electronic indicator 76 that displays the left or right position of
the steerable wheel 12.
[0029] In another method of measuring the steerable wheel position,
an active steering system 100 is used in the vehicle 10a. Since the
vehicle 10a with the active steering system is similar to the
previously described vehicle 10 in FIG. 1, similar parts appearing
in FIG. 1 and FIG. 10, respectively, are represented by the same,
corresponding reference number, except for the suffix "a" in the
numerals of the latter. With the active front steering system 100,
the vehicle 10 comprises a powered actuator 102 controlling the
steering angle 24a in combination with a driver input control angle
measured on the steering wheel 44a. The active front steering
system 100 includes an active front steering controller 104 in
operable communication with the powered actuator 102. The powered
actuator 102 is operably connected to the steering column 36a via a
coupler 106. The active front steering system 100 assists in
pivoting the steerable wheels 12a. Although a particular kind of
active front steering system 100 is described herein, other systems
known in the art may be utilized. In basic operation, the active
front steering system 100 alters (positively or negatively) the
driver input control angle from the driver as applied to the
steering wheel 44a, via the powered actuator 102. The steering
angle 24a as defined by the steerable wheel 12a is determined by a
combination of the driver input control angle and an additional
steering angle supplied by the powered actuator 102. The active
front steering controller 104 could include the controller 16 (or
communicate with the controller 16 (not shown)) to provide the
position of the wheel 12a and to switch the wheel position
indicator between the on state and the off state. The wheel
position as supplied by the wheel position indicator 14a could be a
function of the combined steering input (i.e., driver input control
angle plus additional steering angle supplied by powered actuator
102) to the vehicle.
[0030] In the present invention, when the digital visual indicator
is used, the controller 16 selectively alters the wheel position
indicator 14 between the on state and the off state by turning the
digital visual indicator on and off for the on state and the off
state, respectively. Therefore, the lights of the digital visual
indicator will represent the position of the steerable wheel when
the wheel position indicator is in the on state and will not
represent the position of the steerable wheel when the wheel
position indicator is in the off state. Alternatively, when an
analog visual indicator is used (e.g., when the visual indicator is
directly connected to the steering column of the vehicle), a back
light of the visual indicator will be turned on when the wheel
position indicator is in the on state and will be turned off when
the wheel position indicator is in the off state. A back light is a
light behind the indicators (e.g., speedometer, odometer, fuel
gauge, etc.) that allows the indicators to be seen. When the wheel
position indicator is in the off state, the back light behind the
visual indicator will be shut off.
[0031] In one embodiment of the present invention, the
predetermined driving condition is when the vehicle 10 is traveling
off of a paved road surface, or in an off road condition. In this
embodiment, the controller 16 communicates with a sensor 150
detecting an operating parameter of the vehicle 10 to determine if
an off road condition is present based upon the operating
parameter. The controller 16 may include a general-purpose
microprocessor-based controller, and may include a commercially
available off-the-shelf controller. The controller 16 preferably
includes a processor and memory for storing and processing software
algorithms which processes inputs from the sensor. If the
controller 16 determines if an off road condition is present, the
controller 16 switches the wheel position indicator to the on
state.
[0032] The following are examples of operating parameters readable
by the sensor 150 and the determination made by the controller 16
to determine that the off road condition is present. First, the
sensor 150 could read a steerable wheel to road friction at high
temperatures, with a low ratio indicating that the vehicle 10 is in
the off road condition. Second, the sensor 150 could read a
vertical acceleration of the vehicle 10 in combination with a speed
of the vehicle 10, with a large vertical acceleration of the
vehicle 10 at low speeds indicating that the vehicle 10 is in the
off road condition. Third, the sensor 150 could read a condition of
differential locks, with an engagement of the differential locks
indicating that the vehicle 10 is in the off road condition.
Fourth, the sensor 150 could read a condition of a low ratio gear
box, with engagement of the low ratio gear box indicating that the
vehicle 10 is in the off road condition. Fifth, the sensor 150
could read a frequency of a load on the steerable wheels 12, with a
dynamic low frequency indicating that the vehicle 10 is in the off
road condition. Sixth, the sensor 150 could read deflections of an
anti-roll bar, with large deflections indicating that the vehicle
10 is in the off road condition. Seventh, the sensor 150 could
receive global positioning satellite (GPS) signals, with the GPS
signals indicating that the vehicle 10 is in the off road
condition. Eighth, the sensor 150 could read a position of a dial
in the vehicle 10 selected by the driver, with the position of the
dial indicating that the vehicle 10 is in the off road condition.
Finally, the sensor 150 could read a difference in a height of the
steerable wheels 12, with a height below a certain level indicating
an on road condition because the vehicle 10 could only be on a
curb, but a number of large wheel travels indicating that the
vehicle 10 is in the off road condition. Although only one
operating parameter reading can be used to determine the condition
of the vehicle 10, more than one operating parameter could be
measured by the sensor 150 or multiple sensors to determine the
condition of the vehicle 10. The sensors, measurements taken by the
sensors and the determinations by the controller 16 listed above
are described for illustrative purposes only and are not meant to
limit the sensors and sensor readings available in the system of
the present invention. The controller 16 would also be able to
determine that the off-road condition is not present using the same
readings as discussed above. The controller 16 would therefore
determine that an on road condition is present.
[0033] In another embodiment of the present invention, the
predetermined driving condition is when the steerable wheel 12 has
a slip angle above or equal to a predetermined amount. The slip
angle is the angle between a plane of the wheel (the central plane
of the wheel, normal to the spin axis) and the direction of travel
of the center of tire contact (the intersection of the wheel plane
and vertical projection of the spin axis of the wheel onto the road
plane). The slip angle as used in the second embodiment could be
set to any desirable slip angle. For example, the predetermined
driving condition would be when the slip angle of the steerable
wheel is above 5.degree.. In the preceding example, the controller
16 would turn the wheel position indicator 14 to the on state when
the wheel slip is at 5.degree. or above and would turn the wheel
position indicator 14 to the off state when the wheel slip is below
5.degree.. Those skilled in the art would appreciate that any other
slip angle could be used for turning the wheel position indicator
14 between the on state and the off state.
[0034] In yet another embodiment of the present invention, the
predetermined driving condition is when the steering angle 24 is
above a certain amount. For example, the wheel position indicator
14 could be turned to the on state when the steering angle 24 is
equal to or above 33.degree. and turned to the off state when the
steering angle 24 drops below 33.degree..
[0035] It will be readily appreciated by those skilled in the art
that modifications may be made to the invention without departing
from the concepts disclosed herein. Such modifications are to be
considered as included in the following claims, unless these claims
by their language expressly state otherwise.
* * * * *